This invention relates to a hydroponic culture system which provides systematic, economical, and very workable hydroponic culture for almost uniform plants.
A conventional art hydroponic culture system has been disclosed in Japanese Patent Publication Laying-open No. 91833/1974. In this system, as shown in FIG. 20, plants are supported on an angle panel 01 having a number of holes; the plants are supplied with sunshine through a transparent arch roof 02, and with a hydroponic solution sprayed onto the roots of the plants from a hydroponic solution spraying mechanism 03 as shown in FIG. 21, to cultivate the plants. The hydroponic solution spraying mechanism 03 is fixed inside the angle panel 01 and is provided with a number of spray nozzles disposed along the longitudinal direction of the angle panel 01 to spray the hydroponic solution to the roots of the plants. The grown plants are harvested by removing panels 01a supporting the plants, as shown in FIG. 22.
The above-described conventional art hydroponic culture system has disadvantages including:
(1) Since sunlight is used as it occurs naturally, the growth rate and the harvest time of the plants vary with climatic or sunshine conditions (duration, direction and intensity of sunshine).
(2) At the harvest the panels 01a must be carried out of the system and new panels 01a are mounted, thus requiring a substantial time for the harvest.
(3) The entire hydroponic solution spraying mechanism is very long and has a number of spray nozzles, thus requiring a large amount of hydroponic solution to be recirculated with a high supply pressure.
(4) To assure a constant spraying pressure for each spray nozzle, the piping design becomes complicated and large in size.
(5) Since there is a substantial distance between the spray nozzles, there occurs a difference in the amount of the hydroponic solution sprayed depending on the position of each nozzle, resulting in different growth rates between the cultured plants.
(6) If some of the spray nozzles become clogged, the spraying operation becomes inconsistent, and there occurs a substantial difference in growth rate of the plants corresponding to the clogged nozzles relative to those corresponding to the normal or unclogged nozzles.
The use of artificial light has been considered to cultivate the plants with a uniform growth rate; however, this method requires a large amount of photo-energy since the lighting efficiency is low, which is impractical from an economical point of view.